Hi again, Even stranger is the fact that the coefficeints (the slope) and the intercepts are not independent, in fact they are directly inversely proportional (r squared = 1). This means that that there isnt a random slope and intercept for each individual (which is what I wanted), but straight line that pivots in the middle and will change from individual to individual. Is there a problem with the way I have structured the random model or a deeper problem with lmer()? here is the code I used m2 <- lmer(changewt ~ newwt+(newwt|id), data = grow) coef(m2) Any suggestions very much appreciated, Simon
> I don't this is because you are using REML. The BLUPs from a mixed model > experience some shrinkage whereas the OLS estimates would not. > >> -----Original Message----- >> From: [EMAIL PROTECTED] >> [mailto:[EMAIL PROTECTED] On Behalf Of Simon Pickett >> Sent: Tuesday, August 15, 2006 11:34 AM >> To: [email protected] >> Subject: [R] REML with random slopes and random intercepts >> giving strange results >> >> Hi everyone, >> I have been using REML to derive intercepts and coeficients >> for each individual in a growth study. So the code is >> m2 <- lmer(change.wt ~ newwt+(newwt|id), data = grow) >> >> Calling coef(model.lmer) gives a matrix with this information >> which is what I want. However, as a test I looked at each >> individual on its own and used a simple linear regression to >> obtain the same information, then I compared the results. It >> looks like the REML method doesnt seem to approximate the two >> parameters as well as using the simple linear regression on >> each individual separately, as judged by looking at graphs. >> Indeed, why do the results differ at all? >> Excuse my naivety if this is a silly question. >> Thanks to everyone for replying to my previous questions, >> very much appreciated. >> Simon Pickett >> PhD student >> Centre For Ecology and Conservation >> Tremough Campus >> University of Exeter in Cornwall >> TR109EZ >> Tel 01326371852 >> >> ______________________________________________ >> [email protected] mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > Simon Pickett PhD student Centre For Ecology and Conservation Tremough Campus University of Exeter in Cornwall TR109EZ Tel 01326371852 ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
